Which of the following best describes flexible scheduling in transit?

Flexible scheduling in transit refers to the practice of adjusting schedules based on varying levels of demand. This approach allows transit systems to respond dynamically to passenger needs, facilitating increased efficiency and improved service reliability. When demand is high, more trips can be offered; conversely, during times of lower demand, services can be reduced or adjusted accordingly. This minimizes wait times for passengers and better allocates resources.

In contrast, fixed time slots for each trip and strict adherence to a timetable are characteristics of traditional rigid scheduling systems, which do not adapt to real-time passenger demand. Passengers choosing their own travel times might suggest flexibility, but without the system adjusting schedules to meet these choices, it does not truly represent flexible scheduling. Therefore, option B captures the essence of flexible scheduling effectively, making it the correct choice.